Yield Limits in the Corn Belt Topic of Latest Science Perspective
Don Ort, Professor of Plant Biology, with Stephen Long, Professor of Crop Sciences and Plant Biology, discuss corn belt yield limits in a recent perspective in Science magazine.
"In total global production, corn (maize, Zea mays L.) is the most important food and feed crop. Of the 967 million metric tons produced in 2013, 36.5% were produced in the United States, mostly in the Midwest Corn Belt. The United States is by far the world's largest corn exporter, accounting for 50% of corn exports globally. Until recently, breeding and management have allowed farmers to increase the number of plants per acre without loss of yield per plant. On page 516 of this issue, Lobell et al. use a detailed data set for farms across the Corn Belt, to show that increasing yields have been accompanied by rising drought sensitivity, with important implications for future crop yields."
Ort and Long go on to explain in greater detail some of the existing conditions, and challenges, that exist:
“Atmospheric water vapor pressure deficit in the corn belt is expected to rise from 2.2 kPa today to 2.65 kPa by 2050. To understand the effect of this increase, consider that today, average precipitation across the study area is 37 inches (940 mm) per year. If we assume that 70% of this water is available to the crop, with the remaining 30% lost in drainage, soil evaporation and runoff, then a VPD of 2.2 kPa would support a yield of 214 bushels per acre. This is more than enough water to support the 2013 average yield of ∼170 bushels per acre but would limit yield in areas receiving less than 25 inches of precipitation. If VPD rises to 2.65 kPa, an average rainfall of 37 inches would only support 192 bushels per acre (see the figure), making production far more vulnerable even to moderate droughts. However, if improved genetics and agronomy can achieve the 70% yield increase to 272 bushels per acre projected to be needed by 2050, this would require 50 inches of precipitation per year. Today, production across the study region is largely rainfed, but meeting these targets would require irrigation. Such a productivity increase is unlikely to be sustainable with respect to water resources.”
Read the full article on the Science website, as well as the Lobell et al. report Greater Sensitivity to Drought Accompanies Maize Yield Increase in the U.S. Midwest.